Without any more info, I would say it's the fuel filter. A clogged fuel filter can handle only so much flow and that will be the same in any gear.

ausie

10-11-2006, 08:26 AM

it could be several things. Like what superG stated, it may also be related to the fuel pressure regulator or fuel pressure sensor.

what happens when it cuts out on you? If it feels like hitting a brick wall it could be leaing out on you which may be related to detonation. Do you have a cold air intake or the stock one? If you have a cold air intake, perhaps clocking the MAF sensor would help (try to get the MAF sensor tube as close to the bend in the CAI as possible). I had a similar issue with my 01 but could not clock the MAF so the cold air intake was removed.

Also, what mods are done to the car? that may help at least identify what may be going on.

O2 sensor failures may cause abrupt issues but usually results in a check engine light flashing. Check the spark plugs for abnormal wear on the electrodes.

Also, the ECU has a spilt timming which occurs at or around 5000 RPM. If your ECU is not working properly the secondary timming curve is not kicking in. It could be related to the timming sensor which is located on the front of the motor next to the crank pully. Since the timming sensor is a hall effect (magnet) it will pick up metal debris and may hinder its performance.

Not quite sure what would cause it to fail at the 4000rpm range since it could be a number of things causing it.

ausie

10-12-2006, 08:07 AM

Also, depending on which model year you have, earlier models have plates that open up the secondary intake ports which probably occurs at that RPM range. Not sure what would happen when they do not open but chances are the it will bog a bit since the engine is not getting the air it needs for the fuel delivered based on the throttle sensor position, it is not that simple but could be the problem you are facing.

Pauls 04

10-12-2006, 12:54 PM

I hate to sound ignorant, but what does "clocking the MAF sensor " mean and what does it do for you????

blk04cobra1

10-12-2006, 08:24 PM

I hate to sound ignorant, but what does "clocking the MAF sensor " mean and what does it do for you????

Your MAF sensor sits on your intake tube...sometimes if it's moved it can throw off your tune or how the car runs...if he had it tuned in one position and it was accidentally moved, then it can affect the tune :thumbsup:

ausie

10-13-2006, 07:35 AM

If you look at the stock air box there are no bends in front of the MAF meter and the MAF sensor is positioned so it remains in the air streem as the trailing part of the intake tube up ward and over to the throttle body. Once you place an aftermarket cold air kit on the intake, most will just place the air filter in the fender. They usually have a large bend in front of the MAF meter and if the meter is connected in the stock position (MAF sensor on top) the air flow may bypass the sensor since it will take the shortest path closer to the bend of the intake pipe. If the Cold air intake uses the stock air meter, you only have 4 positions to clock the meter. Clocking the meter is by reattaching it to the inlet tube so that the MAF sensor is on one of the sides or on the bottom. If you rotate the MAF meter so that the MAF sensor is closer to the bend in front of it may correct the problem. IF you have the stock intake you cannot clock the MAF meter since it only attaches in a fixed position. Clocking the meter only applies to aftermarket cold air intake systems. Improper air flow metering may result in poor performance and increases the potential for detonation. This would be followed by damage to the head gaskets or worse. The better CAI systems should have been flow tested to ensure the proper placement of the MAF sensor. Actually it becomes far more complicated to fine tune the MAF sensor position unless you could monitor the change in voltage under variations of throttle position.

99blackcobra

10-20-2006, 10:55 AM

I would do the easy things first. Take some Carb cleaner that is safe for sensors. Then clean up all the O2 sensors. Then buy some SeaFoam and either pour into gas tank or run it through a vacuum line. This will clean up your lines,intake, and injectors of carbon built up. After you do this then change the fuel filter. Take a fuel pressure gage and attach to the rail then rev the engine. You can get a cleaner to clean the mass air flow also. I believe more than anything it is a fuel pump starting to get weak. I had the same problem in my 94 mustang gt.

flynfink

10-20-2006, 04:33 PM

trolling?

ausie

10-21-2006, 12:03 PM

One thing that may be the issue is the IMRC (intake manifold runner controls) which can be found on the 4.6L from 96 up to 98. Cleaning them may be the answer to your problems but will require removal of the fuel rails and intake plenum. I did a search on "ford imrc" and found several links and attached one below. More than likely it is a varnish build up on the IMRC's since they are lacking a fuel injector on the runners connected to them to keep them clean.

Once you get them cleaned up, and if that cures the issue, you may want to use cleaners on a regular basis to prevent the buildup

I saw a can of this at work (amsoil power foam) and should ask my friend how well it works. Below is the link to the product and it is used to clean internals of the motor.

https://www.amsoil.com/storefront/apf.aspx

Sea foam will do the similar task but will be difficult to get the IMRC's cleaned unless you remove the plenum. Too bad that you cannot just remove the fuel injector and spray it into the port since the secondary ports that have the IMRC valves on them do not share the same runner as the one with the injector on it.

As a rule to follow, any time you use parts cleaners on intakes, valves, etc.... it is best to follow the cleaning with an oil change in case some of the solvents pass by the rings on the pistons and contaminate the oil.

There is one other solvent that most do not know about or it becomes neglected since there are products on the shelves of automotive stores that claim to be the cleaners of choice. This solvent is perfect for removing tar and road grim off of the tail pipes (nothing comes close). It can even be used to clean out throttle bodies provided that you remove them from the intake first. This solvent is gasoline. Just use the same amount of caution when using it as a cleaner as you would with the other products that typically contain ether (most throttle body cleaners use ether as a solvent since it evaporates quickly).